On the basis of comparative morphological and physiological studies in the fishes and anuran amphibians, we are attempting to find correlations between structure and function in the inner ear that might in turn shed light on mechanical and mechano-electric aspects of auditory and vestibular transduction. Scanning electron microscope studies of surface morphology are being carried out in organs whose sensory responses are known or have been strongly inferred (e.g., amphibian papillae of Rana catesbeiana, Bufo americana, and Scaphiopus sp., the utricles of certain skates and rays, and the like). In addition, electrophysiological studies are being carried out to verify the responses of the putative gravistatic organs of the frog, where many of the details of surface morphology already have been worked out. In extensions of these previous studies, the inner ear of the frog is being fixed under sustained acceleration in an attempt to observe morphological changes correlated with stimulus in the gravistatic organs.